1. Field of the Invention
The invention relates to valve seat inserts for inlet valves of reciprocating internal combustion engines.
2. Brief Description of the Prior Art
A conventional valve seat insert for an inlet valve of a reciprocating internal combustion engine comprises an annular valve-engaging surface extending around an aperture whose periphery is defined by an edge of the valve seat insert. The aperture is of circular cross-section and is centered on the axis of the annular valve-engaging surface.
Conventional valve seat inserts are therefore axi-symmetrical, and the flow of charge into the cylinder when the valve is open therefore also tends to be axi-symmetrical, within limits imposed by the shape of the combustion space. It is an object of the present invention to provide a new form of valve seat insert which, at least in certain cases, improves the operation of the engine. In a particular case, a substantially reduced fuel consumption and improved starting characteristics have been found.